Lighting Design Glossary

Radiant Flux
Radiant Power

(Terms of radiometry)

Radiant flux is radiant energy per unit time.

As all radiation related terms, this is not very
intuitive to understand.
If we use an analogy of flowing water, then the
energy relates to the absolute amount of water
travelling a certain vertical distance, while the
flux or power is the fraction of this amount
travelling the same distance in a given time.

Standard unit for radiant flux is Watt (W),
which is defined as Joules per Second (J/sec).